Review of papers regarding vacuum system and materials

M. Wong, 21-Mar-02

 

This review summarizes the outgassing rates of various materials:

 

        Aluminum

        Stainless steel

        Epoxies

        Kapton

        Plastics

 

Also described are the results of various cleaning methods.

 

Chart 1 summarizes the outgassing rates of aluminum. Note the different methods of measurement and treatment of samples.

 

Material

Treatment

Outgassing rate

(torr-L/sec-cm2)

Time meas.

(hours)

Test method

Reference

Year

Aluminum

None

1x10-6

1h

 

Schamus (ref Markley, et al)

1999

Aluminum

Degassed

1.7x10-7

1h

 

Schmaus (ref Markley, et al)

1999

Aluminum

Degassed

2.7x10-8

10h

 

Schmaus (ref Markley, et al)

1999

Aluminum

6061-T6

Baked 13.5h @ 300C

1.4x10-8

10h

 

Schmaus (ref Das)

1999

Aluminum

Cleaned

8x10-9

10h

 

Schmaus (ref Blears, et al)

1999

Aluminum

Fresh, degreased w/ trichloroethylene & cleaned w/ ethyl alcohol

6.3x10-9

1h

conductance

Elsey (ref Schram)

1975 (1963)

Aluminum

Degassed

4.6x10-9

100h

 

Schmaus (ref Markley, et al)

1999

Aluminum

6061-T6

Baked @ 200C

4.5x10-9

10h

 

Schmaus (ref Das)

1999

Aluminum

Degassed 24h, degreased w/ trichloroethylene & cleaned w/ ethyl alcohol

4.14x10-9

1h

conductance

Elsey (ref Schram)

1975 (1963)

Aluminum

6061-T6

None

2.5x10-9

10h

 

Schmaus (ref Das)

1999

Aluminum 5083-O

Bell jar, as received, room temp.

2.18x10-9

10.3h

Rate-of-rise

Schrank, et al

1964

Aluminum 5083-O

Bell jar, as received, room temp.

1.27x10-9

8h

Conductance

Schrank, et al

1964

Aluminum 5083-O

Bell jar, as received, room temp.

6.6x10-10

24h

Conductance

Schrank, et al

1964

Aluminum 5083-O

Bell jar, as received, room temp. after baking @ 220C

4.6x10-10

50h (baked @27-31h)

Conductance

Schrank, et al

1964

Aluminum

6061-T6

Baked 15h @ 300C

1.6x10-10

10h

 

Schmaus (ref Das)

1999

Aluminum

Degassed 24h, degreased w/ trichloroethylene & cleaned w/ ethyl alcohol

3.06x10-10

1h

conductance

Elsey (ref Schram)

1975 (1963)

Aluminum 5083-O

Bell jar, no. 4 finish (lapped), room temp.

2.87x10-10

6.0h

Rate-of-rise

Schrank, et al

1964

Aluminum

Fresh, degreased w/ trichloroethylene & cleaned w/ ethyl alcohol

6.0x10-10

10h

conductance

Elsey (ref Schram)

1975 (1963)

Aluminum, type 1100

Cleaned w/ detergent, rinsed w/ acetone, pumped 24 hours

~10-10

0

conductance

Young

1968

Aluminum

LEP vacuum chamber, chem.. clean, baked in situ @ 150C

2.3x10-11

24h

 

Mathewson, et al

1988

Aluminum 6061-T4

Degreased in acetone w/ methanol rinse; baked 100C

6x10-12

24h

Rate-of-rise & conductance

Halama, Herrera

1976

Aluminum 6061-T4

Degreased in acetone w/ methanol rinse, chem polished, baked 100C

3x10-12

24h

Rate-of-rise & conductance

Halama, Herrera

1976

Aluminum 6061-T4

Degreased in acetone w/ methanol rinse, chem polished, glow discharge in Ar, baked 100C

5x10-13

24h

Rate-of-rise & conductance

Halama, Herrera

1976

Aluminum, type 1100

Above plus baked 15h @ 250C under vacuum

4x10-13

24h @ room temperature

conductance

Young

1968

Aluminum

PETRA vacuum chamber, glow discharge@145C

1x10-13

Up to 200h

In situ glow discharge, conductance

Mathewson, et al

1977

 

Chart 2 summarizes the outgassing rates of stainless steels, along with the surface treatment and pumping time.

 

Material

Treatment

Outgassing rate

(torr-L/sec-cm2)

Time meas.

(hours)

Test method

Reference

Year

Stainless steel

None

6.4x10-7

1h

 

Schamus (ref Markley, et al)

1999

Stainless steel

degreased

4x10-7

1h

 

Schamus (ref Markley, et al)

1999

Stainless steel

None

2x10-7

1h

 

Schamus (ref Blears, et al)

1999

Stainless steel

None

2x10-8

10h

 

Schamus (ref Blears, et al)

1999

Stainless steel NS22S

Fresh

1.4x10-8

1h

Conductance

Elsey (ref Schram)

1975

Stainless steel ICN 472

fresh

1.3x10-8

1h

Conductance

Elsey (ref Schram)

1975

Stainless steel

None

1.2x10-8

10h

 

Schamus (ref Das, et al)

1999

Stainless steel ICN 472

sanded

8.3x10-9

1h

Conductance

Elsey (ref Schram)

1975

Stainless steel NS22S

electro polished

4.3x10-9

1h

Conductance

Elsey (ref Schram)

1975

Stainless steel NS22S

mechanically polished

1.7x10-9

1h

Conductance

Elsey (ref Schram)

1975

Stainless steel

fresh

1.5x10-9

10h

Conductance

Elsey (ref Schram)

1975

Stainless steel ICN 472

Polished & vapor degreased

1.4x10-9

10h

 

Schamus (ref Dayton, et al)

1999

Stainless steel

None

1.4x10-9

10h

 

Schamus (ref Das, et al)

1999

Stainless steel NS22S

fresh

1.3x10-9

10h

Conductance

Elsey (ref Schram)

1975

Stainless steel ICN 472

sanded

1.0x10-9

10h

Conductance

Elsey (ref Schram)

1975

Stainless steel

None

7.6x10-10

1h

 

Schamus (ref Das, et al)

1999

Stainless steel NS22S

mechanically polished

4.6x10-10

10h

Conductance

Elsey (ref Schram)

1975

Stainless steel NS22S

electro polished

4.3x10-10

10h

Conductance

Elsey (ref Schram)

1975

Stainless steel

Baked 24h @ 200C

1.5x10-10

1h

 

Schamus (ref Das, et al)

1999

Stainless steel

None

1.1x10-10

100h

 

Schamus (ref Das, et al)

1999

Stainless steel 304

Degrease + water rinse

4.0x10-11

40h

Conductance

Strausser

1973

Stainless steel U15C

Baked 25h @ 300C

4.5x10-12

 

 

Elsey (ref Calder, et al)

1975

Stainless steel 304

Degrease + water rinse, baked in vacuum 150C for 12h

4.0x10-12

5h after bakeout

Conductance

Strausser

1967

Stainless steel 304

Electropolished, baked 30h @ 250C

3.0x10-12

 

 

Elsey (ref Young)

1975

Stainless steel U15C

Baked 45h @ 360C

2.6x10-12

 

 

Elsey (ref Calder, et al)

1975

Stainless steel

Baked 24h @ 200C

9.3x10-13

100h

 

Schamus (ref Das, et al)

1999

Stainless steel U15C

Baked 3h in vacuum @ 1000C + 25h in situ @ 360C

1.6x10-14

 

 

Elsey (ref Calder, et al)

1975

 

Other cleaning methods are listed in Chart 3, although outgassing rates are not measured:

 

Material

Treatment

Results

Reference

Year

Aluminum

Quench a hot aluminum extrusion in an Ar-O2 atmosphere

Dense, thin (~20 thick) oxide layer

Sasaki, Y.T.

1990

Aluminum 6063

Clean with an alkaline detergent (Almeco 18)

Removes MgO, C, and Al2O3

Sasaki, Y.T.

1990

Aluminum

Vapor degreasing, pump for 120h before and after bake

Dominant residual gases: H2O, H2, CO, CO2, & CH4; after baking @ 150C and pumping, H2O & CH4 gone, outgassing rates of other gases reduced 1 order of magnitude except H2

Mathewson, A.G., et al

1989

Aluminum

Vapor degreasing, then light alkaline etch (CERN basic procedure), pump for 120h before and after bake

Dominant residual gases: H2O, H2, CO, & CO2; after baking @ 150C and pumping, only H2 exists

Mathewson A.G., et al

1989

Aluminum

Strong alkaline etching in NaOH, pump for 120h before and after bake

Dominant residual gases: H2O, H2, CO, CO2, & CH4; after baking @ 150C and pumping, only H2 exists

Mathewson A.G., et al

1989

Aluminum

Vapor degreasing, Ar glow discharge @ 150C

On initiation of discharge, large pressure increase (normal in Ar glow discharge) was too large for accurate measurement

Mathewson A.G., et al

1989

Aluminum

Vapor degreasing, then light alkaline etch (CERN basic procedure), Ar glow discharge @ 150C

H2, CO dominant gases desorbing from surface during discharge cleaning

Mathewson A.G., et al

1989

Aluminum

Strong alkaline etching in NaOH, Ar glow discharge @ 150C

H2, CO dominant gases desorbing from surface during discharge cleaning at order of magnitude less than light alkaline etch

Mathewson A.G., et al

1989

SS

H2 glow discharge - 22C

Dominant residual gases: CH4, CO, & C2H4; water production insignificant; frequent arcing on all exposed surface noted during initial discharge period

Dylla, H.F.

1988

SS

H2 glow discharge 150C

Dominant residual gases: CH4, CO, & C2H4, and H2O; frequent arcing on all exposed surface noted during initial discharge period

Dylla, H.F.

1988

SS

Ar glow discharge ambient temp

Dominant residual gases that were significantly removed: CO2, H2

Dylla, H.F.

1988

SS

Ar/O2 glow discharge

Improved removal of CO and CO2; minor amts of implanted Ar that can be removed by baking @ 350C

Dylla, H.F.

1988

 

Ar/O2 glow discharge 2h, exposed to air, then Ar/O2 glow discharge 2h

Some degree of passivation: residual gases were removed with 1st cleaning & did not show up during the 2nd cleaning

Dylla, H.F.

1988

 

O2 glow discharge

Rapid removal of carbon, not of hydrocarbons (which can be baked out initially), increased surf. Oxidation, sputtering of the base metal, and possible enhanced outgassing of O2-containing molec.

Dylla, H.F.

1988

 

 

Chart 4 shows different outgassing measurements of epoxies.

 

Material

Treatment

Outgassing rate

(torr-L/sec-cm2)

Time meas.

(hours)

Test method

Reference

Year

NMA w/ solid alumina filler

Cured 300F

1.6x10-7

 

 

Hanson, Patel

1970

Polyimide polymer

Thermosetting; measured @ 40C

~1.1x10-7

4h+9min

conductance

Kendall, Zabielski

1965

Polyimide polymer

Thermosetting; measured @ 155C

~5x10-8

4.5h increase temp + 6h

conductance

Kendall, Zabielski

1965

Silicone resin

Needs dicumyl peroxide catalyst; thermosetting, measured @ 35C

~5x10-8

4h

conductance

Kendall, Zabielski

1965

Araldite epoxies

Cured ~150C for 15h

~10-8

51h pumping

conductance

Barton, Govier

1965

 

Kapton is a newer material and little data exists about its outgassing rate. Below are three references.

 

Material

Treatment

Outgassing rate

(torr-L/sec-cm2)

Time meas.

(hours)

Test method

Reference

Year

Kapton cable

 

1.0x10-5

0h

conductance

Postma

1999

Kapton foil

 

1.0x10-7

40h

 

Ferro-Luzzi

1999

Polyimide

Bake @ 300C

4.0x10-8

12h

 

Weston

1970

Kapton cable

 

2.4x10-8

168h

conductance

Postma

1999

Kapton cable

 

2.7x10-9

336h

conductance

Postma

1999

Kapton cable

 

6.5x10-10

504h

conductance

Postma

1999

 

Chart 6 shows the outgassing rates of several types of plastics.

 

Material

Treatment

Outgassing rate

(torr-L/sec-cm2)

Time meas.

(hours)

Test method

Reference

Year

Nylon

 

1.2x10-5

1h

 

Elsey (ref Power, et al)

1975

Nylon

 

6.0x10-6

1h

 

Elsey (ref Power, et al)

1975

PVC

24h @ 95% relative humidity

8.5x10-7

1h

conductance

Elsey (ref Santler)

1975

PTFE

Fresh

1.7x10-7

1h

conductance

Elsey (ref Santler)

1975

Teflon

 

6.5x10-8

1h

conductance

Elsey (ref Santler)

1975

PTFE

Fresh

3.3x10-8

10h

conductance

Elsey (ref Santler)

1975

Teflon

 

2.5x10-8

10h

conductance

Elsey (ref Santler)

1975

PVC

24h @ 95% relative humidity

2.0x10-8

10h

conductance

Elsey (ref Santler)

1975

G-10

 

~10-8

 

 

Beams Division - FNAL

2001